I'm just curious why human couldn't deliver their babies by themselves?? I've read one source and it said that it's because that we, human have evolved by standing with two extrimities, not four extrimities (like commonly primates)...and this situation makes our cingulum pelvicum(I don't know what the English is.. ) getting smaller and make us hard to deliver our babies....
Is it true? or any different causes?

Q: Why are chemists great for solving problems?
A: They have all the solutions.

I've heard that too. I think standing on two legs means that the pelvis has much more weight to support. This means it needs to be more robust so it can't separate so much during child birth. Passing the baby through the pelvis probably causes more damage in humans than other animals due to the tighter fit. It's also harder due to the large size of the head compared to other animals.

Also, being social animals (with medical care) there is no selection to be able to give birth unaided.

hmm...based on the magazine that I read, the coelom in human pelvic bone is getting narrower since human begins to walk with two feet..

- advantages
efficiency of energy.
free their anterior extremity.
longer move distance (helping out in moving to other continents).

- disadvantages
back hurts (or other back problems).
for women, difficulity in baby delivering.
many foot problems.
a thinner cortex bone layer in certain bone at foot area (means that our bone is more spongeous than our 4 feet ancestors)... .

Q: Why are chemists great for solving problems?
A: They have all the solutions.